1. Field of the Invention
This invention relates to the manufacture of crimped cellulose fibre and particularly to the crimping of cellulose fibre that has been made by a method comprising the spinning of continuous cellulose filaments from a solution of cellulose in an organic solvent, particularly an amine oxide solvent. Cellulose manufactured in this manner is known as lyocell and will hereinafter be referred to as solvent-spun cellulose or lyocell. The invention is also concerned to provide useful short, i.e. staple, fibre lengths from the crimped continuous filaments.
2. Description of the Related Art
The manufacture of lyocell cellulose filaments is described in, for example, U. S. Pat. No. 4,416,698 the contents of which are incorporated herein by way of reference. This Patent discloses a method of producing cellulose filaments by dissolving the cellulose in a suitable solvent such as a tertiary amine N-oxide.
A hot solution of the cellulose is extruded or spun through a suitable die assembly including a jet to produce filamentary material which is passed into water to leach out the amine oxide solvent from the extruded filaments.
The production of artificially formed filaments of material by extruding or spinning a solution or liquid through a spinnerette to form the filaments is, of course, well known. Initially, relatively small numbers of individual filaments were prepared, which filaments were individually wound up for use as continuous filament material. This meant that the number of continuous filaments which needed to be produced was essentially dictated by the number of filaments which could be individually wound either before or after drying.
However, if fibre is produced as a tow or if fibre is produced as a staple fibre then different criteria apply to the number of filaments which can be produced at any one time. A tow essentially comprises a bundle of essentially parallel filaments which are not handled individually. Staple fibre essentially comprises a mass of short lengths of fibre. Staple fibre can be produced by the cutting of dry tow or it can be produced by forming a tow, cutting it whilst still wet, and drying the cut mass of staple fibre.
Because there is no need to handle individual filaments in the case of a tow product or a staple product, large numbers of filaments can be produced simultaneously.
Thus the tow of cellulose filaments is cut before or after drying to form the desired mass of short lengths of staple fibre.
Natural cellulose fibres have a natural crimp, which is advantageous in providing frictional properties when the fibres are put to use, e.g. directly for non-woven products or for the production of yarns from woven or knitted products. Lyocell, however, does not have an inherently natural crimp.
It is, therefore, an object of the present invention to provide fibre from lyocell cellulose filaments in which the fibre has a crimp applied to it.